Events & Seminars

2018 Jun 25

HD-Combinatorics Special Day: "Quantum ergodicity and spectral theory with a discrete flavour" (organized by Elon Lindenstrauss and Shimon Brooks)

(All day)

Location: 

Feldman Building, Givat Ram
Title for the day: "Quantum ergodicity and spectral theory with a discrete flavour"

9:00-10:50: Shimon Brooks (Bar Ilan), "Delocalization of Graph Eigenfunctions"
14:00-15:50: Elon Lindenstrauss (HUJI), "Quantum ergodicity on graphs and beyond"

See also the Basic Notions by Elon Lindenstrauss @ Ross 70 (16:30).

Abstract for morning session:
2018 Jun 19

T&G: Yaron Ostrover (Tel Aviv), Quantitative symplectic geometry in the classical phase space.

12:00pm to 1:30pm

Location: 

Room 110, Manchester Buildling, Jerusalem, Israel
We shall discuss several topics regarding symplectic measurements in the classical phase space. In particular: Viterbo's volume-capacity conjecture and its relation with Mahler conjecture, the symplectic size of random convex bodies, the EHZ capacity of convex polytopes (following the work of Pazit Haim-Kislev), and (if time permits) also computational complexity aspects of estimating symplectic capacities.
2018 Jun 18

HD-Combinatorics: Special day on sparsification (by Ilan Newman and Yuri Rabinovich)

(All day)

Location: 

Eilat Hall, Feldman Building, Givat Ram

Special day on sparsification
Speakers: Ilan Newman and Yuri Rabinovich.

Part I:   10:30 - 12:30
Part II:  14:00 - 15:50

Abstract for the day:
Time permitting, we plan to discuss the following topics (in this order):

1.
* Additive Sparsification and VC dimension
* Multiplicative Sparsification
* Examples: cut weights, cut-dimension of L_1 metrics, general metrics,
                    and their high-dimensional analogues

2.
2018 Jun 14

Basic Notions: Elon Lindenstrauss (HUJI) : Effective Equidistribution of closed orbits, property tau, and other applications

4:00pm to 5:15pm

Location: 

Ross 70
Ergodic theoretic methods in the context of homogeneous dynamics have been highly successful in number theoretic and other applications. A lacuna of these methods is that usually they do not give rates or effective estimates. Einseidler, Venkatesh and Margulis proved a rather remarkable quantitative equidistribution result for periodic orbits of semisimple groups in homogenous spaces that can be viewed as an effective version of a result of Mozes and Shah based on Ratner's measure classification theorem.
2018 Jun 25

Elon Lindenstrauss (HUJI) - Effective Equidistribution and property tau

4:30pm to 5:45pm

This is the second of two lectures on the paper Einseidler,, Margulis, Mohammadi and Venkatesh https://arxiv.org/abs/1503.05884. In this second lecture I will explain how the authors obtain using property tau (uniform spectral gap for arithmetic quotient) quantitaive equidistribution results for periodic orbits of maximal semisimple groups. Surprisingly, one can then use this theorem to establish property tau...
2018 Jun 20

CS Theory -- Erdős Lecture: Igor Pak (UCLA) "Counting Young tableaux"--CANCELLED

Lecturer: 

Igor Pak (UCLA)
10:30am to 12:00pm

Location: 

Rothberg (CS building) B-220

The number of standard Young tableaux of skew shape is a mesmerizing special case of the number of linear extensions of posets, that is important for applications in representation theory and algebraic geometry.  In this case there is a determinant formula, but finding their asymptotics is a difficult challenge.  I will survey some of the many beautiful result on the subject, explain some surprising product formulas, connections to Selberg integral, lozenge tilings and certain particle systems.

2018 Jun 12

T&G: Sara Tukachinsky (IAS), An enhanced quantum product and its associativity relation

1:00pm to 2:30pm

Location: 

Room 110, Manchester Buildling, Jerusalem, Israel
Open Gromov-Witten (OGW) invariants count pseudoholomorphic maps from a Riemann surface with boundary to a symplectic manifold, with constraints that make sure the moduli space of solutions is zero dimensional. In joint work with J. Solomon (2016-2017), we defined OGW invariants in genus zero under cohomological conditions. In this talk, also based on joint work with J. Solomon, I will describe a family of PDEs satisfied by the generating function of our invariants. We call this family the open WDVV equations.
2018 Jun 11

HD-Combinatorics: Aner Shalev, "Probabilistically nilpotent groups"

10:00am to 10:50am

Location: 

Feldman Building, Givat Ram
In the past decades There has been considerable interest in the probability that two random elements of (finite or certain infinite) groups commute. I will describe new works (by myself and by others) on probabilistically nilpotent groups, namely groups in which the probability that [x_1,...,x_k]=1 is positive/bounded away from zero. It turns out that, under some natural conditions, these are exactly the groups which have a finite/bounded index subgroup which is nilpotent of class < k. The proofs have some combinatorial flavor.

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